This application responds to RFA CA-92-02, which addresses the staging of non-CNS solid pediatric tumors. The following specific aims will be achieved: 1. Determination of the relative sensitivities and specificities of computerized tomography (CT), and magnetic resonance imaging (MRI) in the detection of direct local spread, regional and distant lymph node metastasis, as well as visceral metastasis. 2. Determination of the relative sensitivity and specificity of MRI in the detection of bone marrow involvement. In subjects with neuroblastoma MRI will be compared to 123-I metaiodobenzylguanidine (123I-MIBG). 3. Comparison of the relative efficacy of CT, MRI, 123I-MIBG, and positron emission tomography (PET), when interpreted alone or jointly, in evaluating response to chemotherapy. Specifically-whether changes in tumor size, signal intensity, Gadolinium enhancement, 123I-MIBG uptake, and 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) uptake on PET scan- correlate with a favorable response to chemotherapy. 4. Determination of whether MRI signal characteristics (intensity measurements using different TR and TE values), Gadolinium enhancement, and PET can be used in distinguishing viable from non-viable tumor and suggest biopsy sites. All subjects will undergo-MRI evaluation of the primary tumor site (enhanced and unenhanced) to encompass the cranial and caudal extension of the tumor, bone marrow, and liver-CT of chest, 99mTc MDP bone scan, 123I-MIBG scan, and 18F-FDG PET imaging. Tumors located in the head and neck region or thoracic and abdominal cavities (including paratesticular region) will also be evaluated by CT. All subjects will undergo these studies at three points in their management: at diagnosis, after chemotherapy induction and at conclusion. The imaging findings will be compared to surgical findings, bone marrow aspirate or biopsy results, and follow-up outcome.